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Molecules in the outermost layers of the atmosphere are always reaching escape velocity - but there is sufficient statistical fluctuation that you will never, ever be able to demonstrate that your shout made a particular molecule escape. Let's do some math. Assuming that your sound wave is still a sound wave (rather than a shock wave) when it leaves your ...


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I'll just give a short outline (many caveats though): Energy in sound waves drops off as the square of the distance (a sound wave spreads out as a sphere from your mouth). If we do not take dissipation into account, you need to compare the maximum energy of your shout and divide it by $R^2$ with $R$ the distance you want to consider. Compare the kinetic ...


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The nonlinear term, $\left( \mathbf{V} \cdot \nabla \right) \mathbf{V}$, determines the steepening of a wave. This can be balanced/offset by loss terms like dispersion, diffusion, viscosity, resistivity, friction, etc. If the loss term dominates over the nonlinear term, then the wave cannot steepen as there is too much damping. If the loss term balances ...


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According to the MTU webpage Speed of Sound in Air, some things to consider: if the ideal gas model is a good model for a real gas, then you can expect, for any specific gas, that there will be no pressure dependence for the speed of sound. This is because as you change the pressure of the gas, you will also change its density by the same factor. ...


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Yes it can be done, and indeed it's a well established technology called active noise control. The idea is based on destructive interference. If at some point two sound waves have the same intensity and frequency and they're 180ยบ out of phase then they will sum to zero and the sound intensity at that point will be zero. Your phrase negative sound just means ...


3

The amplitude/intensity of a sonic boom (in Earth's atmosphere) is dependent on the change in pressure across the shock wave. This should make sense, as the intensity of a sound wave is dependent upon its pressure relative to quiet periods. We also know that the ratio of the downstream to upstream pressure is proportional to the square of the Mach number. ...


2

The shock wave from a supersonic object is a cone composed of overlapping spherical wavefronts. As individual wavefronts form, they propagates radially outward at speed $c$ (speed of sound) and have a radius $ct$. At the same time the object traveling at speed $v$ moves forward $vt$. The angle of the vertex of the of the shock wave is known as the Mach angle ...


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Typically it is the ferrite cores in inductors/transformers that resonate mechanically, or through magnetostrictive effects that produce a high pitched whine. Switching PSUs are the main culprit. It can also occur when the EM fields interact with steel components in the PSU.


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Here are some topics to read about: Frequency doubling, also called second-harmonic generation as Johannes mentions. Here, you put one wave into a medium, and some fraction of it is converted to a wave with a different frequency. By carefully engineering the medium you can get quite a high conversion percentage. Other nonlinear optical processes, not just ...


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Floris, great answer. The confusion in the question is a really common one that isn't emphasized enough in teaching. Intuitive View Here's an easy way to remember this: When the speaker pushes, the air touching the speaker moves one way. When the speaker pulls, the air touching the speaker moves the other way. Put more formally, for each movement of the ...


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Although normally considered as photon interactions, any inelastic scattering process will result in the alteration of the frequency of the electromagnetic radiation. An obvious example is Compton scattering, where high energy (X-rays+) light scatters from free electrons. The scattered light has lower energy and longer wavelengths than the light incident ...


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If you have a small diapragm moving slowly then the air will just flow around it and you won't get any appreciable pressure rise in front of the diaphragm. That means there won't be any longitudinal pressure waves (i.e. sound waves) generated normal to the diaphragm surface. If you now make the diaphragm larger the air has farther to move to get to the ...


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Intensity is defined to be the average energy passing through a unit area per second. The key here is average. By defining it this way, we avoid intensity that varies with every period. The average intensity doesn't change unless the source changes it. In calculating the intensity the r.m.s. average pressure is calculated, and this is proportional to ...


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The actual shock wave is quite short lived (I think it's visible for less than a second near 0:14 as a white sheet around the smoke/dust cloud) and doesn't propagate very far in this case. When the shock dissipates what's left is a pressure wave, the "bang" or sonic boom, and that propagates at the speed of sound. So I guess your video uses a reasonable ...


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The Rayleigh waves in question are a kind of evanescent wave. At least this is what happens in a surface acoustic wave filter - a neat device that converts electrical signals into acoustic ones and then back again by the piezo-electric effect, allowing the designer the exploit the low acoustic velocity to realise complex filter responses from the wave ...


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Bulk acoustic waves - like the one in the quartz piezo-electric in watches or on computer chips are typically launched perpendicular to the surface by a bulk transducer. More generally, however, In a material with one or more parallel, flat surfaces, the modes of the system can all be classified by their frequencies $\omega$ and in plane two-component ...


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The answer is the two are very close, but there are theoretical differences. It is VERY hard to construct actual scenarios where linear acoustic diffraction differs substantially from the diffraction of light. As noted already, linear acoustic waves are scalar pressure fields, whereas electromagnetism is a vector phenomenon, i.e. there is a polarisation ...



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